In aqueous solutions maintained at pH 2.5, 5-Azacytidine (5-AC) forms a prodrug with sodium bisulfite. The prodrug is approximately 10 times more stable at pH 2.5 than 5-AC. The prodrug reverts back to 5-AC at physiological pH's. The prodrug has potential for a stable parenteral dosage form or an oral dosage form of 5-AC.